devel/adacurses: Fix linking options on adacurses.gpr
The options weren't getting sent to the linker. Moreover, the -lncurses
switch was not required and runpath switches are required, otherwise
the realtime linker finds the system libncurses before the ports version.
Use "Linker_Options" instead of "Switches" to enable linker options.
Reported by: Natacha Porte

devel/adacurses: Build it properly; switch to original sources
This was another Ada "library" port that didn't actually build the
library. The first step is to switch to the original source (AdaCurses
has been distributed by ncurses, but it's maintained separately by
Thomas Dickey). Besides a much smaller distfile, we also get the html
documentation which is not provided by ncurses.
Use the provided makefile to build. The only change was adacurses.gpr
added by myself to use as an alternative to adacurses-config (which is
also now generated instead of provided if /files). This should address
a complaint I heard at FOSDEM about AdaCurses not working (hopefully).